For mobile processor based systems, including, for example laptop computers, personal digital assistants, and smart devices such as game devices or multi-function communication devices, it is advantageous to reduce power consumption both to prolong battery life and to reduce processor generated heat. One method to achieve this is to design a processor of the system to lower the minimum voltage at which the processor operates.
Processors may include an on-die cache to improve performance. The Random Access Memory (RAM) cells of the cache may limit the lowest possible voltage at which the processor may be operated. This is because RAM cells in on-die processor caches are manufactured from devices typically designed to the smallest possible size supported by the fabrication process used to manufacture the processor, and the devices are, as a side effect, very sensitive to variations that normally occur during manufacturing, causing a few cells to deviate significantly from the average in terms of the minimum voltage required for them to operate correctly. Therefore, in order to ensure that all the cells in the on-die cache operate correctly, the minimum operating voltage of the processor core is often set to a value that meets or exceeds the maximum value required by those few cells, and thus may be significantly higher than the value that would be required to ensure the operation of a normally manufactured or average cell in the cache.